Skip to content Skip to navigation
University of Warwick
  • Study
  • |
  • Research
  • |
  • Business
  • |
  • Alumni
  • |
  • News
  • |
  • About

University of Warwick
Publications service & WRAP

Highlight your research

  • WRAP
    • Home
    • Search WRAP
    • Browse by Warwick Author
    • Browse WRAP by Year
    • Browse WRAP by Subject
    • Browse WRAP by Department
    • Browse WRAP by Funder
    • Browse Theses by Department
  • Publications Service
    • Home
    • Search Publications Service
    • Browse by Warwick Author
    • Browse Publications service by Year
    • Browse Publications service by Subject
    • Browse Publications service by Department
    • Browse Publications service by Funder
  • Help & Advice
University of Warwick

The Library

  • Login
  • Admin

Estimating the space density of ultracompact binary stars

Tools
- Tools
+ Tools

Carter, P. J. (Philip J.) (2014) Estimating the space density of ultracompact binary stars. PhD thesis, University of Warwick.

[img]
Preview
PDF
WRAP_THESIS_Carter_2014.pdf - Submitted Version - Requires a PDF viewer.

Download (20Mb) | Preview
Official URL: http://webcat.warwick.ac.uk/record=b2745569~S1

Request Changes to record.

Abstract

The AM Canum Venaticorum (AM CVn) binaries are a rare group of hydrogen-deficient, ultrashort period, mass-transferring white dwarf binaries, some of which may be Type Ia supernova progenitors. These systems represent the end product of several finely-tuned evolutionary pathways, and as such are of great interest for binary stellar evolution theory. They are also some of the strongest known sources of low-frequency gravitational waves. Establishing their space density is important for constraining evolutionary models, and the signals we expect to detect from the Galactic population. This has been difficult as much of the known population has been discovered in a heterogeneous manner.

In this thesis I present the latest results from a spectroscopic survey designed to uncover the hidden population of AM CVn binaries in the photometric database of the Sloan Digital Sky Survey (SDSS). This small, colour-selected sample of ∼2000 candidates, is expected to contain the majority of all AM CVn binaries in the SDSS. The survey is now approximately 70 per cent complete, and the discovery of only seven new AM CVn binaries indicates a lower space density than previously predicted.

Characterisation of the sample requires detailed follow-up observations after the initial discovery, in order to determine the orbital period. I present time-resolved spectroscopy of the recently-discovered AM CVn binary SDSS J173047.59+554518.5, and the dwarf nova SBSS 1108+574. The orbital period I measure for SDSS J1730 confirms its ultracompact binary nature. The quiescent spectrum of SBSS 1108+574 is unusually rich in helium compared to typical cataclysmic variables (CVs). I find that its orbital period is significantly below the normal CV period minimum. This indicates that the donor in SBSS 1108+574 is highly evolved, making it a candidate for the often-dismissed ‘evolved CV’ channel for AM CVn binary formation.

I discuss a wider search for new AM CVns in the SDSS spectroscopic database, and present two new systems discovered in SDSS-III spectroscopy. Since this search has revealed only these two new systems, it is unlikely that we have missed a large population of AM CVn binaries, and their discovery should have little effect on our previous calculations of the AM CVn space density.

Item Type: Thesis or Dissertation (PhD)
Subjects: Q Science > QB Astronomy
Library of Congress Subject Headings (LCSH): Double stars, White dwarf stars
Official Date: April 2014
Dates:
DateEvent
April 2014Submitted
Institution: University of Warwick
Theses Department: Department of Physics
Thesis Type: PhD
Publication Status: Unpublished
Supervisor(s)/Advisor: Marsh, T. R. ; Steeghs, D. (Danny), 1972-
Extent: xii, 165 leaves : charts
Language: eng

Request changes or add full text files to a record

Repository staff actions (login required)

View Item View Item

Downloads

Downloads per month over past year

View more statistics

twitter

Email us: wrap@warwick.ac.uk
Contact Details
About Us